Interphase and Percolation

The simplest immiscible polymer blend has three phases matrix polymer 1, dispersed polymer 2, and an interphase between them. The thickness of the interphase ranges from 2 nm (immiscible blends) to 60 nm (reactively compatibi-lized blends) and it may constitute the key-phase for the rheological behavior [3]. 

The first theoretical modeling of polymer blends was carried out by Helfand and his colleagues [25-27]. Their lattice theory approximated the polymer 1-polymer 2 interactions via the Huggins-Flory binary parameter, Xrt-The derivation provided expressions for the concentration gradient across the interface, as well as for the interfacial tension coefficient, Vi2, and the interphase thickness, Al  

Vi2 l is independent of Xi2, the theory predicts a universal reciprocity between the interfacial tension coefficient and the thickness of the interphase. While the prediction is correct for binary systems, it breaks down upon compatibilization (especially reactive compatibilization). The theory also implies that  

These implications are important for understanding the flow behavior of immiscible blends. 

The principal goal of compatibilization is modiflcation of the interphase -reduction of the interfacial energy and thus an increase in its thickness (29, 30]. Tang and Huang proposed a semiempirical equation [31]  

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